It's not really fan ART but Matt Lenz sent me a selection from a Triquetra Cats/Kingdom Hearts crossover fanfic. Here it is...

For two people, it had started out as a very normal night, find
food/target, devour said target, and moan about how the ones with the
power to kill their kind still roamed free and they were the ones
taking the heat for it to happen, then they had to cross paths.

"Gahhh!" Melissa was not used to saying that, normally it was her
dinner date doing so at this point. But now having taken a taste test,
she was clawing at her own tongue to get the flavor off. It reminded
her of tar and acid, mixed in with ashes.
Riku cursed looking at the chunk of himself missing out of his body
mass, dripping black icor, emulating the reaction of pain rather than
really experiencing it. After all, pain was the mark of something
alive, and Riku, well, he wasn't really dead, but it was hard to define
something alive that had no internal heart beat and a body that took in
heat rather than give it off.
But what truly stunned him was his empty hand, an outside observer
would have just seen Riku push his hand into Melissa's chest like he,
or she was a ghost at the same time she had taken a bit out of him.
Pushing her back, Riku couldn't believe his hand held no prize. This
woman was no shadow, but she had no heart!
"What are you?" Riku raised an eye brow.